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5,334 result(s) for "Sand dunes."
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The ecology of sandy shores
The Ecology of Sandy Shores provides the students and researchers with a one-volume resource for understanding the conservation and management of the sandy shore ecosystem. Covering all beach types, and addressing issues from the behavioral and physiological adaptations of the biota to exploring the effects of pollution and the impact of man's activities, this book should become the standard reference for those interested in Sandy Shore study, management and preservation. * More than 25% expanded from the previous edition* Three entirely new chapters: Energetics and Nutrient Cycling, Turtles and Terrestrial Vertebrates, and Benthic Macrofauna Populations * New sections on the interstitial environment, seagrasses, human impacts and coastal zone management* Examples drawn from virtually all parts of the world, considering all beach types from the most exposed to the most sheltered
Linking species and functional diversity to leaf traits during sand-dune stabilization in the Mu Us Desert
Background Understanding the dynamics of species and functional diversity and their interrelationships during vegetation restoration is essential for assessing the effectiveness of ecosystem restoration. Yet, the mechanistic links between species diversity and functional diversity during vegetation restoration remain uncertain, with community-level functional traits likely mediating this relationship. Methods We studied a chronosequence of Artemisia ordosica -dominated dryland communities, including semi-fixed (D1), fixed (D2), soil-biocrusted fixed (D3), and shrub-herbaceous-fixed sand-dunes (D4). Thirteen leaf functional traits were measured, including leaf tissue density (LTD), and leaf dry matter content (LDMC). Community-weighted mean leaf functional traits (CWM-LFTs) were calculated using importance value-weighted averages. Results Species and functional diversity increased progressively from stages D1 to D4, with the coefficient of variation for CWM-LFTs ranging from 7.71% to 57.27%. Changes in species diversity during sand dune stabilization were linked to a strategy of slow growth and cumulative increases in LTD, LDMC, and leaf carbon content (LCC), improving the community’s physical defense and nutrient retention. Leaf structural traits mirrored diversity patterns, with LDMC most strongly linked to functional evenness, functional divergence and Rao’s quadratic entropy. Conclusions Our results show that both species and functional diversity increased progressively with sand-dune stabilization. The plant community followed a trajectory of increasingly complex strategies, shifting from stress-tolerant traits toward competition-adapted traits in later stages. The LDMC was strongly correlated with both species and functional diversity, serving as a key trait that mediates competitiveness and defense in resource-limited ecosystems. These findings highlight the importance of trait-based assembly in vegetation restoration and offer new insights for desertification control.
Nourishing Waters, Comforting Sky
In the Nebraska Sandhills, ranchers on horseback and in pickup trucks share the range with pronghorn antelope, burrowing owls, and long-billed curlews. The native grasses grow greener as the cattle grow fatter. Throughout the region, river otters and mink swim in streams nourished by springs bubbling up from the High Plains (Ogallala) aquifer. Over years of close observation, Stephen R. Jones has gotten to know the Nebraska Sandhills-the twenty-thousand-square-mile expanse of stunning prairie and thriving wetlands. He has felt the warm breath of a white-tailed doe guarding her spotted fawn, learned to communicate with a family of long-eared owls, and developed an improbable hiking relationship with a wild turkey. He has documented a breeding bird population that is growing more diverse and witnessed the long-awaited return of nesting trumpeter swans. These personal stories, accompanied by words of insight from Native American leaders, Sandhills ranchers, and grassland ecologists, help us envision a quiet relationship with the natural world.
Sand dune mobility under climate change in the Kalahari and Australian deserts
Vegetation cover on sand dunes mainly depends on wind power (drift potential—DP) and precipitation. When this cover decreases below a minimal percentage, dunes will start moving. It is therefore necessary to study the effects of DP and precipitation on contemporary dune activity in order to predict likely future dune mobility in the coming decades. We concentrate on the future activity of the currently fixed dune fields of the Kalahari and the Australian deserts. These sand seas include the largest areas of stabilized dunes in the world, and changes in their mobility have significant economic implications. Global maps of DP are introduced, based on real and reanalysis data. Analyses of two global circulation models (GFDL and CGCM3.1) provide future predictions under the SRES-A1B IPCC scenario, which is a moderate global warming scenario. According to the GFDL model, both the Australian and Kalahari basin dunes will apparently remain stable towards the end of the 21st century because the DP will stay small, while the rate of precipitation is expected to remain much above the minimal threshold necessary for the vegetative growth that leads to dune stabilization. The CGCM model predicts insignificant changes in DPs and shows that the precipitation rate is above 500 mm/year for almost the entire Kalahari basin. The central-northern part of Australia is predicted to have larger DPs and greater precipitation than the southern part. Since the predicted changes in DP and precipitation are generally not drastic, both the Australian desert and Kalahari basin dunes are not likely to become active. Still, the Australian dunes are more likely to remobilize than the Kalahari ones due to some decrease in precipitation and an increase in wind power.
Invasion at the Edge: The Case of Rosa rugosa (Rosaceae) in Italy
The Japanese Rose (Rosa rugosa) is a perennial shrub belonging to the family Rosaceae. It was introduced in Europe from East Asia as an ornamental plant in the XIX century and is now considered an invasive species, especially in northern Europe, colonising the Atlantic and Baltic coastal dune habitats and threatening local biodiversity. However, little is known about its presence and invasion patterns in the Mediterranean area. In Italy, R. rugosa has been classified as naturalised and just a few observations have been recorded in dune habitats in the North Adriatic coast. Here, we review the published data on R. rugosa in Europe and present preliminary data on the invasive pattern of R. rugosa on the Italian North Adriatic coast. We surveyed the coastline in two locations (i.e., Brussa and Bibione, Italy) where we characterised the dimension and structure (i.e., number of ramets and stem height) of the R. rugosa populations and listed the associated floristic composition. No occurrence of R. rugosa was recorded in Bibione, probably due to the success of the restoration project carried out on that site. In contrast, several stands of R. rugosa were found in Brussa, where many other alien species were also found (accounting for 15.28% of the sampled species). Given the strong invasiveness of R. rugosa, it is important to keep data on its distribution up-to-date and investigate its ecology and physiology to promote appropriate management strategies to control its spread and anticipate its future potential distribution.
Long‐term sand dune spatio‐temporal dynamics and endemic plant habitat extent in the Athabasca sand dunes of northern Saskatchewan
The Athabasca sand dunes in northern Saskatchewan and north‐east Alberta are a unique landscape of moving sand that hosts nine narrowly distributed endemic vascular plant taxa. We modeled the extent of habitat for each species, corresponding dune morphologies in species habitat, spatial and temporal variation in dune environments, and rates of woody vegetation encroachment at dune boundaries to support an assessment of long‐term threats for the Athabasca endemic dune flora. Landsat images were used to maximize the time spans and areal coverage of the study. The Athabasca sand dunes are currently active and characterized morphologically by crescentic ridge and morphodynamically by transverse form dunes. Longitudinal sand movement parallel to the dune axis resulted in the creation of new dune areas along the east and south‐east boundaries of the dune fields at a rate of 0.14 km2 year−1. Forest succession along the western boundaries of the dune fields resulted at an annual dune loss of 1.98 km2 year−1. The net extent of dune stabilization between 1985 and 2014 was 53.76 km2 or nearly 20 percent of the total open sand dune extent. All habitat modeling methods showed robust performance (>0.5 AUC), with the best performance in most cases from generalized linear models. Estimated total available/occupied habitat was comparatively low for the least abundant species Achillea millefolium (38.92 km2) and Armeria maritima (48.82 km2), and of those areas 53.5% and 16.29%, respectively, are influenced by dune stabilization. Continuing stabilization of the Athabasca sand dunes region may present conservation concerns for these narrowly distributed endemic taxa. This paper addresses the conservation concern of nine narrowly distributed endemic vascular plant taxa in the Athabasca Sand Dunes, Saskatchewan, Canada. We evaluated the extent of critical habitat for each species, dune morphologies, long‐term dune environment spatio‐temporal variation and rates of woody vegetation encroachment at dune boundaries to support a long‐term threats assessment for the Athabasca endemic flora. Remote sensing and GIS were key aspects of the study and Landsat images were used to maximize the time spans and areal coverage of the study. By estimating the distribution of the rare endemic taxa, we were able to show that a large proportion of the area of occupancy of some species is influenced by dune stabilization. Continuing stabilization of the Athabasca sand dunes region may present conservation concern for these narrowly distributed endemic taxa.
GNSS NRTK, UAS-Based SfM Photogrammetry, TLS and HMLS Data for a 3D Survey of Sand Dunes in the Area of Caleri (Po River Delta, Italy)
Coastal environments are fragile ecosystems threatened by various factors, both natural and anthropogenic. The preservation and protection of these environments, and in particular, the sand dune systems, which contribute significantly to the defense of the inland from flooding, require continuous monitoring. To this end, high-resolution and high-precision multitemporal data acquired with various techniques can be used, such as, among other things, the global navigation satellite system (GNSS) using the network real-time kinematic (NRTK) approach to acquire 3D points, UAS-based structure-from-motion photogrammetry (SfM), terrestrial laser scanning (TLS), and handheld mobile laser scanning (HMLS)-based light detection and ranging (LiDAR). These techniques were used in this work for the 3D survey of a portion of vegetated sand dunes in the Caleri area (Po River Delta, northern Italy) to assess their applicability in complex environments such as coastal vegetated dune systems. Aerial-based and ground-based acquisitions allowed us to produce point clouds, georeferenced using common ground control points (GCPs), measured both with the GNSS NRTK method and the total station technique. The 3D data were compared to each other to evaluate the accuracy and performance of the different techniques. The results provided good agreement between the different point clouds, as the standard deviations of the differences were lower than 9.3 cm. The GNSS NRTK technique, used with the kinematic approach, allowed for the acquisition of the bare-ground surface but at a cost of lower resolution. On the other hand, the HMLS represented the poorest ability in the penetration of vegetation, providing 3D points with the highest elevation value. UAS-based and TLS-based point clouds provided similar average values, with significant differences only in dense vegetation caused by a very different platform of acquisition and point of view.
Analysis of Sand Dune Migration and Future Trends on the Western Edge of the Kumtag Desert
Sand dune migration, as a typical dynamic process of aeolian geomorphology in arid regions, directly influences regional ecological security and infrastructure development. Focusing on the western edge of the Kumtag Desert, this study uses remote sensing imagery and field investigations, combined with multi-factor meteorological observations and CMIP6 climate scenarios, to quantitatively analyze the migration characteristics and influencing factors of representative dunes, and to construct a predictive model for future migration trends. The dominant migration direction is W–WNW–NW, which closely matches the composite resultant drift potential. The average annual migration speed is 12.86 m·a−1, classifying these dunes as fast-moving; small to medium dunes migrate faster (13.84 m·a−1) than large dunes (11.27 m·a−1). Wind speed, sand-moving wind frequency, drift potential (DP), Vegetation Fractional Cover (FVC), and precipitation significantly affect migration speeds; wind speed is the primary driver (single-factor R2 = 0.41), while precipitation (R2 = 0.26) and FVC (R2 = 0.27) exert a suppressing effect, particularly on small to medium dunes. Based on stepwise multiple regression analysis combined with CMIP6 multi-model predictions, under the SSP8.5 scenario, characterized by significant temperature increases, drastic fluctuations in precipitation patterns, and notable increases in wind speed, the average annual sand dune migration speed is projected to reach 18.59 m·a−1 by the end of this century, an increase of 5.78 m·a−1 compared to the current speeds; whereas under the SSP1–2.6 and SSP2–4.5 scenarios, changes are projected to be minor and overall relatively stable. The findings of this study provide a scientific basis for regional infrastructure and engineering planning, as well as for the renovation and protection of existing oil and power transmission lines.
DIVERGENCE IS FOCUSED ON FEW GENOMIC REGIONS EARLY IN SPECIATION: INCIPIENT SPECIATION OF SUNFLOWER ECOTYPES
Early in speciation, as populations undergo the transition from local adaptation to incipient species, is when a number of transient, but potentially important, processes appear to be most easily detected. These include signatures of selective sweeps that can point to asymmetry in selection between habitats, divergence hitchhiking, and associations of adaptive genes with environments. In a genomic comparison of ecotypes of the prairie sunflower, Helianthus petiolaris, occurring at Great Sand Dunes National Park and Preserve (Colorado), we found that selective sweeps were mainly restricted to the dune ecotype and that there was variation across the genome in whether proximity to the nondune population constrained or promoted divergence. The major regions of divergence were few and large between ecotypes, in contrast with an interspecific comparison between H. petiolaris and a sympatric congener, Helianthus annuus. In general, the large regions of divergence observed in the ecotypic comparison swamped locus-specific associations with environmental variables. In both comparisons, regions of high divergence occurred in portions of the genetic map with high marker density, probably reflecting regions of low recombination. The difference in genomic distributions of highly divergent regions between ecotypic and interspecific comparisons highlights the value of studies spanning the spectrum of speciation in related taxa.